Shock absorbing strut



Filed Aug. 15, 1940 AAAR MM A ,A Aw.. `A t A C .A A L Rl .n A7 N 4 mw R s N o mk EF AA A|A A A WN A A Il Tlf... IIH l. WY /A l I 4 @uf A A A i a AA 6 a Al A s 2 ...AMA s A A ,s .d 4 A/ A A AA4 u I 7 H A 3 A 4 A A A n AJA 5 HA A 5 2 I e aan an... .n ./Q 4 a, m .A .4222 a v i A N n. i I A n i. A A .A AV lA .A mi A n l A 2A A 4 v4 a n In the modiiication shown in Fig. 5, the valve 43 has been omitted and the valve 50 replaced by an intake and exhaust valve including a housing 54 also screwed within the cap II.' Within the outer end of this housing there is provided a cupshaped bushing 55 having an enlarged orifice 56 to resist the action of the compressed air on the ball 49 until the air in the compartments 31 and I has reached a predetermined pressure which iscalculated to actas a cushion for normally reextending through the ybottom thereof throughl which is free to slide the rod 51 of a poppet valve 58, which valve is seated against a movable seat 59, which itself is seated against the housing 54 as clearly shown in Fig. 5. Betweenv the bottom' of the bushing 55 and the headBO of the rod 51, there is a light compression spring 6I, and a heavier compression spring 62 between the bushing 55 and the movable seat 59. The housing 55 is closed by an apertured cap 63 screwed on the bushing 55 which extends from the housing 54.,`

yInpractice, the shock absorbing strut, while fully compressed,.is partly lled with liquid suchas oiluntil its level reaches the inner end ofthe filler tube 38. into the compartment 36 through the i'lller tube 40 by way of the airvalve 4l until the air within that compartment has reached a predetermined of the inner cylinder I5fwill engage the piston 33 for moving this piston upwardly, thereby subjecti'ng the compressedair within thev compartment 38, to additional. compressionk which will retard Vand `rfinally check further compression of` the strut.

`Uponl taking off, that is, when the landing wheel 32 leaves the ground, the weight of the landing wheelv as well as that of the inner cylinder I5,vwill tend to cause'the fullV extension of the strut.`- Normally, the "increase in the Volumetric capacity of the compartment 31 resulting Compressed air is also admitted tarding the compression of the struts upon landing of the craft.

In the modification shown in Fig. 5, upon extension of the strut or more specifically downward movement of the inner cylinder I5 in the compartment 31, the poppet valve 58, when subjected to initial vacuum within the compartment 5l of the tube I 2, will move downwardly away from the seat 59vby compressing the relatively light compression spring 6I, thereby enabling intake of atmospheric air through the valve into the tube I2 or its compartment 5I and the compartment 31 through the ports 52. Upon compression of the strut, the air in the compartment 31 being compressed due to a reduction inthe volumetric capacity of that compartment will flow in the compartment 5I through the ports 52 and act on the poppet valve 58 causing it together with the seat 59 to move away Vfrom the p housing 54 to enable exhaust of the compressed from the downward stroke of the inner cylinder f I5,'would create at least a 'partial vacuum in the.

compartment 31, which would rtend to prevent full extensionv of the strut. With the valveV 43,

when a predetermined lvacuum is created within the compartment 31, the ball wil1 move into open position relative to the port 44 by compressing thev spring 48 and allowV intake of atmospheric air intor the compartment 31, thereby `breaking the vacuum existing in this compartment and enabling full extension of the. strut. y d Whenfit is desiredvto retract the landing gear, the strut is first compressed by adequate mecha-v nism (not shown) vpulling the cylinder l5 into the compartment 31 until the inner end of the cylinder I5 engages the piston 33. In this in stance, the atmospheric air previously admitted into the compartment 31 through the intake,y

valve 43 will of course be subjected to compression due to a reduction in thel volumetric capacity of the compartment 31. Normally this (com-4 pressed air would prevent the retraction Vof the strut.;` With the .valve 41, the compressed air vformed in the compartment 31 iiowing into the compartment 5I` of the tube I2. throughthe ports 52,A will act on thelball 49` to compress theA spring 50 and enable exhaust ofthe compressed air through the valve port 48 as shown in Fig. 3.

The compression of the spring 50. is calculated air through the housing. In this instance, the spring k69 is also calculated to resist action of the 'compressed air on the seat 59 until it has reached a predetermined pressure.

From the foregoing description, it will be understood that extension of the strutcan be afpartments 31 and 5I due to a reduction in the' volumetric` capacity of these compartments is neverthelessA possible by providing the check valve r41 which automatically allows the compressed air to exhaust from the compartment 5I 4 whenthe pressure thereof has reached a predetermined maximum.

Although the foregoing description is necessarily of a detailed character, in order to completely set forth the invention, it is to be understood that the specific terminology is not intended to be restrictive or confining and it is to be further understood that various rearrangements of parts and modifications of structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

`I claim:

In a shock absorbing strut for aircraft, a pair of tubular members one surrounding the other and having a closed upper end, an upper and a lower compartment between said members separated by a slidable 'piston,` compressible iiuid within the upper compartment, a landing wheel carrying cylinder slidable in the lower compartcluding a valve controlled port through the closed upper end of the inner member enabling exhaust `of said air only when subjected to a predetermined pressure resulting from'the inward movement of said cylinder.

JOHN F. WALLACE. 

